Code From Getting Started With Hooks - ReactKHI Meetup #02

HooksExample.js

import React, { useState, useEffect } from 'react';

const Counter = () => {
  // initial state.
  const initialState = {
    counter: 0
  };

  const [state, setState] = useState(initialState);

  // increament the counter
  const increament = () => {
    setState({
      counter: state.counter + 1
    })
  }

  useEffect(() => {
    // Update the document title using the browser API
    document.title = `You clicked ${state.counter} times`;
  });

  // sets the interval
  useEffect(() => {
    const timerID = setInterval(() => {
      increament();
    }, 1000);
    return () => clearInterval(timerID);  // cleaup function
  });

  return (
    <div>
      {state.counter}
    </div>
  );
}

export default Counter;